Primary choriocarcinoma of the urinary bladder: a case report.

We present a 37-year-old patient with primary choriocarcinoma arising in the urinary bladder, who received 5 months of intensive chemotherapy with a very good response. He died of a pulmonary embolus before his treatment could be completed. A post-mortem examination revealed extensive necrotic nodules in the lungs and brain. There was only one small focus of viable tumour in the brain. There was no residual tumour in the bladder, and no testicular tumours or scars fulfilling the criteria for a true extragonadal teratoma. It is likely that the origin of the bladder choriocarcinomas is from metaplasia/de-differentiation of a transitional cell carcinoma to the level of trophoblast. Lesser degrees of differentiation producing functional changes in the carcinoma cells with secretion of beta hCG without structural changes are much more common.